A reinforced plastic is a material obtained by incorporating fiber made of any of various materials into a plastic in order to compensate lack of strength and thermal resistance of the plastic. As the reinforced plastic, there are known, for example, a glass fiber-reinforced plastic {GFRP: the fiber (reinforcing material) is glass fiber}, a carbon fiber-reinforced plastic {CFRP: the fiber (reinforcing material) is carbon fiber}, a boron fiber-reinforced plastic {BFRP: the fiber (reinforcing material) is boron fiber}, and metal fiber {MFRP: the fiber (reinforcing material) is metal fiber}.
The carbon fiber-reinforced plastic is utilized for aerospace materials, sporting goods (golf, tennis rackets), and the like because of its excellent characteristics, such as tensile modulus of elasticity.
The glass fiber-reinforced plastic is utilized for building materials and the like because of its characteristics, such as incombustibility and thermal resistance.
Meanwhile, there is a problem in that waste treatment and recycling of the carbon fiber-reinforced plastic and the glass fiber-reinforced plastic are difficult owing to their excellent characteristics.
In order to solve the problem, the following patent applications have been reported.
In Patent Literature 1, there is a disclosure of a “recovery method for reclaimed carbon fiber, characterized in that when a carbon fiber-reinforced plastic is subjected to carbonization treatment in a carbonization furnace to recover reclaimed carbon fiber, a ground product containing the carbon fiber-reinforced plastic at a maximum diameter of 20 mm or less is placed in the carbonization furnace so as to have a layer thickness of 300 mm or less, and while an inert gas is introduced at from 10 times/minute to 100 times/minute with respect to an internal volume of the furnace, the carbonization treatment is performed under a furnace pressure of from 0.3 mmH2O to 1.0 mmH2O at a treatment temperature of from 400° C. to 950° C.”
However, the recovery method disclosed in Patent Literature 1, in which the carbonization treatment is performed, is obviously different from a recovery method of the present application.
In Patent Literature 2, there is a disclosure of a “recovery method for carbon fiber in a carbon fiber-reinforced plastic, including pressurizing and heating a mixture of a carbon fiber-reinforced plastic with tetralin or decalin under a non-oxidizing gas atmosphere to decompose and remove a resin in the carbon fiber-reinforced plastic.”
However, the recovery method disclosed in Patent Literature 2, in which the mixture with tetralin or decalin is used, is obviously different from the recovery method of the present application.
In Patent Literature 3, there is a disclosure of a “method of recovering glass fiber from a fiber-reinforced plastic, characterized by bringing a fiber-reinforced plastic including glass fiber and a polymer arranged to cover the glass fiber into contact with semiconductor powder at 100° C. or more in the presence of oxygen to remove the polymer through oxidative decomposition, to thereby recover the glass fiber.”
However, Cr2O3 powder is the only semiconductor powder that has been actually demonstrated to enable recovery of the glass fiber. In addition, there is also a mention of titanium oxide, but only powder titanium oxide is applicable.
In recent years, there have been proposed various methods of treating and recycling plastic waste, and further, parts thereof have been practically employed. As a potent one of such methods of treating plastic waste, there has been proposed an apparatus and method involving gasifying the plastic waste by heating chips of the plastic waste in the presence of a decomposition catalyst of titanium oxide known as a photocatalyst (see Patent Literatures 4 and 5).
In addition, various catalysts to be used in decomposition treatment of the plastic waste have been investigated (Patent Literatures 6 to 11).